1. Field of the Invention
The present invention is drawn to implantable hearing devices in general and more particularly to totally implantable electronic hearing devices which bypass the ossicular chain of the middle ear by connecting the vibrations of the tympanic membrane directly to the parilymph fluid of the inner ear through a self-contained electronic amplification assembly.
2. Description of the Prior Art
Totally implanted electronic hearing devices are known wherein the electronics consisting of the power pack, sensor, amplifier and transducer are located within a hollowed out portion of the skull such as the mastold cavity. These devices use microphones to pick up the sound in the outer ear by way of a tube connected to the microphone from the outer ear. The sound is then amplified and sent to a transducer which is connected to the ossicular chain which in turn transmits this amplified signal to the inner ear through the oval window. An example of such a device is found in U.S. Pat. No. 3,882,285 by Nunley, et al.
Other devices use microphones located Just under the skin behind the outer ear to receive audio signals and transmit them to the middle ear. Examples of such devices are found in U.S. Pat. Nos. 3,346,704 and 3,557,775.
These forementioned devices all transmit their amplified signals to the ossicular chain of the middle ear which in turn activates the inner ear by way of the oval window. The ossicular chain thus adds a mass which must be activated by the amplified signal and thus acts as an energy sink for the amplified signal.
Other devices require disarticulation of the ossicular chain. Thus a more sensitive device was needed which would bypass the normally functioning existing ossicular chain and only add an additional amplified signal of tympanic membrane vibrations directly to the inner ear.